The present invention relates to a method of fitting closable opening devices to respective sealed packages for pourable food products, and to packages featuring such devices.
Many pourable food products, such as fruit juice, UHT (ultra-high-temperature processed) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of such a package is the parallelepipedal package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is formed by folding and sealing laminated strip packaging material. The packaging material has a multilayer structure comprising a layer of fibrous material, e.g. paper, covered on both sides with heat-seal plastic material, e.g. polyethylene; and, in the case of aseptic packages for long-storage products, such as UHT milk, the packaging material comprises a layer of oxygen-barrier material, defined for example by an aluminium film, which is superimposed on a layer of heat-seal plastic material and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.
As is known, such packages are produced on fully automatic packaging machines, on which a continuous tube is formed from the strip-fed packaging material; the strip of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution; following sterilization, the sterilizing agent is removed, e.g. vaporized by heating, from the surfaces of the packaging material; and the strip of packaging material so sterilized is kept in a closed sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is then filled with the sterilized or sterile-processed food product, and is sealed and cut at equally spaced cross sections into pillow packs, which are subsequently folded mechanically to form finished, e.g. substantially parallelepipedal, packages.
Alternatively, the packaging material may be cut into blanks, which are formed on forming spindles into packages which are then filled with the food product and sealed. One example of such a package is the so-called xe2x80x9cgable-topxe2x80x9d package known as Tetra Rex (registered trademark).
Packages of the above type are normally provided with closable opening devices by which to pour, and prevent external agents from coming into contact with, the food product in the package.
Such opening devices substantially comprise a frame defining an opening and fitted to a hole or a punch-through or pull-off portion in a wall of the package; and a cap hinged to the frame.
The cap is normally molded integrally with the frame, and is originally sealed to the frame, along a peripheral edge about the opening, by a thin breakable annular connecting portion. Once unsealed, the cap is movable between a closed position, cooperating in airtight manner with the frame, and an open position.
Alternatively, threaded caps are used, which are separate from and originally screwed to the frame, and which are normally molded integrally with respective tamper-evidence rings connected coaxially to the caps by breakable radial connecting portions.
The above caps are pressed onto the respective frames so that the respective tamper-evidence rings click onto respective annular base flanges of the frames and past the thread portions of the frames close to the flanges.
One problem posed by the opening devices described lies in the cap having to be easily detachable from the frame when unsealing the package. For which purpose, the opening device is made of low-break-strength plastic material, normally polyethylene.
As polyethylene, however, is a poor oxygen barrier, the side of the packaging material eventually forming the inside of the package must be fitted, over the hole, with an additional xe2x80x9cpatchxe2x80x9d defined by a small sheet of heat-seal plastic material, and the opposite side of the packaging material must be fitted with an oxygen-barrier member, e.g. a pull-off tab, heat sealed to the patch and comprising a layer of aluminium.
Providing barrier members and patches calls for additional processing of the packaging material before the material is sterilized and folded and sealed to form the vertical tube, thus increasing the manufacturing time and cost of the package. More specifically, the packaging material must be fed successively through a cutting station for forming the holes; a first sealing station for applying the patches; and a second sealing station for applying the barrier members to the respective patches.
Moreover, besides opening the cap, the user also has to remove the barrier member to open the package.
It is an object of the present invention to provide a method of fitting a closable opening device to a sealed package for pourable food products, designed to eliminate the aforementioned drawbacks typically associated with known methods.
According to the present invention, there is provided a method of fitting a closable opening device to a sealed pourable food product package having at least one removable portion; said opening device comprising a frame defining a pour opening, and a removable cap fitted to said frame to close said opening; said method comprising the step of causing said frame to adhere to said package about said removable portion; and being characterized by also comprising the step of causing said cap to adhere directly to said removable portion of said package.
The present invention also relates to a sealed pourable food product package having at least one removable portion and provided with a closable opening device, which comprises a frame defining a pour opening and fitted to the package about said removable portion, and a removable cap fitted to said frame to close said opening; characterized in that said cap comprises an anchoring portion fixed directly to said removable portion.